In recent years, people have been increasingly interested in maintaining or improving their health. Hence, it is desired that one can more easily obtain biological information such as a pulse rate and an electrocardiogram in a daily life for health management. Patent Document 1 discloses a cellular phone that can detect biological information in the normal process of using the phone. Further, Patent Document 2 discloses a cellular phone that allows a user to measure biological information such as body temperature.
The cellular phone disclosed in Patent Document 1 includes galvanic skin reflex (GSR) sensors arranged on the side surface portions of the two peripheral surfaces, corner portions, or the operation surfaces of input buttons, of the cellular phone. Hence, with this cellular phone, biological information can be obtained through normal operations, for example, for voice communication and email communication, i.e., without performing explicit operations for obtaining the biological information.
On the other hand, the cellular phone disclosed in Patent Document 2 includes a contact detection unit that has a pair of electrodes and detects the contact state of a human body and a temperature detection unit for measuring body temperature as biological information of a human body, arranged on the right side surface of the casing of the main body. With this cellular phone, information about the body temperature of a user detected by the temperature detection unit is obtained when it is detected that the user is in contact with the temperature detection unit on the basis of a current flowing through the pair of electrodes forming part of the contact detection unit. Hence, with this cellular phone, body temperature information is automatically obtained while a user is in contact with the contact detection unit without performing a special operation, such as an operation of turning on a measurement initiation switch.    Patent Document 1: International Publication No. 2005/048832    Patent Document 2: Japanese Patent No. 4119863
As described above, with the cellular phone disclosed in Patent Document 1 and the cellular phone disclosed in Patent Document 2, the biological information of a user can be obtained while the user is holding the cellular phone and performing normal operations, such as an operation of entering/selecting a telephone number and an operation of writing an electronic mail. However, even when a biosensor is provided at a position with which the hand of a user is in contact while the user is operating a mobile apparatus such as a cellular phone, during actual operations, a portion other than a finger used for the operations will also move together with the finger, thereby causing a problem in that noise is superimposed on the output signal of the biosensor.
In particular, when a measured portion is a portion of a hand which performs the operation, noise superimposed on the sensor output signal may become larger than a biosignal, thereby making the measurement impossible. In addition, when a pulse rate and a heartbeat are measured, obtaining of data in real time or obtaining of continuous data over a relatively long time (for example, about ten seconds to several minutes) is required in many cases, thereby causing an increase in the influence of body movement noise.